1. Field of the Invention
The present invention relates to an apparatus and a method for driving a display panel with a temperature compensated driving voltage, and more particularly, to an apparatus and a method for driving a display panel by dividing a temperature range into predetermined temperature sections and outputting different driving voltages for the respective predetermined temperature sections.
2. Description of the Related Art
A liquid crystal display (LCD) panel controls transmissivity of a liquid crystal of the LCD in response to video data that is to be displayed as an image corresponding to the video data. When a driving voltage corresponding to the video data is applied to the electrodes of the LCD panel, the molecules of the liquid crystal of the LCD placed between the electrodes are rearranged in response and, thus, the transmissivity of the liquid crystal of the LCD panel is controlled. The luminance of the image corresponding to the video data is determined by the degree to which back light transmits through the liquid crystal of the LCD panel and the color of the image is determined by color filters through which the back light that has transmitted through liquid crystal is input thereto, such that the image is displayed on the LCD panel.
A variation in the temperature of the liquid crystal of the LCD panel rearranges the characteristics of the liquid crystal of the LCD panel. That is, when the temperature of the liquid crystal of the LCD panel varies, the transmissivity and threshold voltage Vth, which is a minimum driving voltage required to rearrange the molecules of the liquid crystal of the LCD panel, change.
FIG. 1 is a graph that illustrates the relationship between the temperature T of the liquid crystal and a driving voltage Vop. The horizontal axis represents the temperature T of the liquid crystal and the vertical axis represents the driving voltage Vop applied to the electrodes of an LCD panel to rearrange the molecules of the liquid crystal of the LCD panel. When the driving voltage Vop varies in response to a temperature variation as illustrated in FIG. 1, the display quality of the LCD panel does not deteriorate due to the temperature variation. That is, the driving voltage Vop corresponds to an ideal driving voltage Vop_Ideal of the LCD panel.
As illustrated in FIG. 1, the ideal driving voltage Vop_Ideal decreases as the temperature T of the liquid crystal of the LCD panel increases. That is, a relatively low driving voltage Vop can control the rearrangement of the molecules of the liquid crystal when the temperature T of the liquid crystal of the LCD panel is high. On the contrary, a relatively high driving voltage Vop can control the rearrangement of the molecules of the liquid crystal of the LCD panel when the temperature T of the liquid crystal is low.
FIG. 2 illustrates a block diagram of an apparatus for driving a display panel with a temperature compensated driving voltage. Referring to FIG. 2, the display panel driving apparatus includes a controller 208, a first driver 206, a second driver 204 and a display panel 202.
The controller 208 controls the driving voltages VopX and VopY in response to a temperature variation. The first driver 206 applies the driving voltage VopX controlled by the controller 208 to an X electrode, e.g., a common electrode of the display panel 202. The second driver 204 applies the driving voltage VopY to a Y electrode, e.g., a segment electrode of the display panel 202, which can be an LCD panel.
FIGS. 3a and 3b illustrate driving voltages that are controlled in response to variations in temperature. A driving voltage Vop having the characteristic curve of FIG. 3a or 3b can drive the display panel of FIG. 2.
FIGS. 3a and 3b illustrate ideal driving voltages Vop_Ideal and temperature-compensated driving voltages Vop_C. The temperature-compensated driving voltage Vop_C of FIG. 3a is linear with a negative slope. When the driving voltage Vop conforms to the temperature-compensated driving voltage Vop_C and is controlled in response to variations in temperature, the adaptivity of the driving voltage Vop to the temperature variation is low because the driving voltage has only one slope. Low adaptivity of the driving voltage to the temperature variation means a large difference between the ideal driving voltage Vop_Ideal and the temperature-compensated driving voltage Vop_C.
The temperature-compensated driving voltage curve Vop_C of FIG. 3b has a plurality of slopes S1, S2, S3, S4 and S5. Specifically, the temperature-compensated driving voltage curve Vop_C has the slope S1 at a temperature less than −10° C., the slope S2 at a temperature between −10° C. and 40° C.°, the slope S3 at a temperature between 40° C. and 60° C.°, the slope S4 at a temperature between 60° C. and 80° C. ° and the slope S5 at a temperature higher than 80° C.°. When the driving voltage Vop conforms to the temperature-compensated driving voltage curve Vop_C of FIG. 3b, the adaptivity of the driving voltage Vop to a temperature variation improves because the driving voltage Vop has different slopes for respective temperature sections. When comparing FIGS. 3a and 3b, the differences between the ideal driving voltage curve Vop_Ideal and the temperature-compensated driving voltage curve Vop_C in FIG. 3b is smaller than it is in FIG. 3a. However, the difference between the ideal driving voltage curve Vop_Ideal and the temperature-compensated driving voltage curve Vop_C is large in temperature sections where the slopes abruptly vary (portions indicated by dotted ovals in FIG. 3b).
Many attempts have been made to reduce the difference between the ideal driving voltage Vop_Ideal and the temperature-compensated driving voltage Vop_C such that the display quality of a display panel does not deteriorate due to variations in temperature.